iZgnsl\%^: }     Colloid  Preparations  in  Medicine.  577 
of  rendering  rabbits  immune  from  anthrax  and  diphtheria  bacilH. 
Again,  colloidall  silver  is  interesting  in  that  it  has  a  selective  germi- 
cidal action  upon  the  pneumococcus  and  the  micrococcus  catarrhalis. 
The  following  fact,  germane  to  the  present  subject,  is  also  of 
great  interest:  The  progress  of  any  ailment  of  bacterial  origin  de- 
pends in  large  measure  upon  the  physical  (electric)  conditions  of 
the  body  fluids  in  which  the  bacteria  reproduce  themselves.  It  is 
possible  so  to  change  these  fluids  (which  we  repeat  are  invariably 
colloidal)  by  the  injection  of  colloids  prepared  in  the  laboratory 
that  the  development  of  the  bacteria  is  hampered  and  the  progress 
of  the  disease  checked.  Here  then  is  a  new  method  of  treating 
contagious  and  infectious  diseases.  Instead  of,  or  supplementary 
to,  vaccines,  serums,  or  ordinary  drugs,  there  is  suggested  the  use 
of  certain  colloids  which  so  act  upon  the  "soil"  in  which  the  bacteria 
grow  that  the  latter  fail  to  develop.  This  branch  of  colloid  therapy 
is  as  yet  in  its  early  infancy,  but  it  needs  no  leap  of  the  imagination 
to  picture  the  possibilities  which  may  be  unfolded  by  research. 
Colloidal  Mktals  and  Non-Mhtals  :  Their  History,  Prepara- 
tion, AND  Properties. — Thos.  Stephenson  contributes  a  resume 
under  this  title.  The  first  publication  in  English  literature  concern- 
ing the  use  of  this  class  of  medicines  is  stated  to  have  appeared  in 
September,  1907.  Graham  first  used  the  word  "colloid"  to  distin- 
guish certain  amorphous  substances,  of  which  glue  and  gelatin  are 
typical  examples,  which  diffuse  with  difficult  through  membranes,  as 
opposed  to  "crystalloids,"  which  diffuse  with  ease.  The  word  is  now 
used  to  describe  a  condition  which  chemical  substances  may  be 
made  to  assume  rather  than  to  define  a  definite  class  of  compounds. 
A  "colloidal  solution,"  or  "sol,"  is  not  a  solution  in  the  strict  sense 
of  the  term,  but  rather  a  suspension  of  minute  particles  of  the  sub- 
stance. 
The  nature  and  properties  of  colloids  and  of  colloidal  sols  have 
been  known  for  some  time,  but  the  assumption  by  the  metals  and 
metalloids  of  the  colloidal  state  is  a  comparatively  recent  discovery. 
It  is  these  that  have  come  into  extensive  use  in  medicine.  The  first 
metal  to  be  used  in  this  way  was  colloidal  silver,  which  was  intro- 
duced in  1896  under  the  name  "collargol."  Collargol  is  sold  in 
the  form  of  small  black  scales  having  a  metallic  luster  forming  with 
water  an  opaque  solution.  It  is  not  really  a  colloidal  metal  but  is 
considered  as  a  combination  of  an  acid  silver  molecule  with  ammonia, 
i.  e.,  collargolate  of  ammonia. 
